I have something 'like tennis elbow, but not exactly the same' according to my GP..
I notice that reach-twist-grip (bass playing) is the most exacerbating. Bizarrely, double bass doesn't have such a bad effect, so hand and arm position has a bearing on this. I've been consciously monitoring the effect of position, and on a 5-string, playing from 5th fret on B rather than open E is definitely less stressful.
Not yet tried the support things, but mean to do so.. there are some specific tennis elbow ones these days, with more particular pressure pads.